Experimental Study On Shear Behavior At Elevated Temperature Of RC Beams Strengthened With High Performance Composite Cement Mortar Laminates Reinforced By Mesh Reinforcements

Fire is playing an important part in the human's life and creating,but once thefire is out of control,it will cause great damage to the human.every kind of fire hascaused a mass of death and great loss of natural resources and materialfortunes.Our country also has many fire accidents in the buildings,and the fireresistance of structures is also an important problem in the filed of structuralengineering.For the filed of structure strengthening,the fire resistance hasbecoming a headachy problem. In the exist strengthening methods,many need touse organic materials such as structural glue,but when the temperature exceed120℃,the strengthening structure will lose its effect as soon as the glue doesn'twork.The strengthening method with the CMMR(composite mortar laminatereinforced with mesh reinforcement) has obvious advantages in the fireresistance ,because the materials it used mainly consist of inorganic materials, thematerial character of which is very similar to the concret,and has good consistent,harmonious and penetrative character with the mother-materials.Based on thesepoints,it will has better fire resistance performance than other strengtheningmethods which use organic structural glue when using CMMR strengtheningmethod.Fire resistance of the RC beams without web strengthened by the CMMR isanalyzed in this dissertation,and also some experiment researches are carriedon.The main contents are summarized as follows.(1) The popular thermal and mechanical behaviors of concret and reinforcedsteel bar at elevated temperature over the world are summarized and compared,atthe same time,experiments are carried on the composite mortar used in thestrengthening method in order to get its regularity of the compressive strength afterelevated temperature.(2) Several special RC specimens strengthened by the CMMR are made tomeasure the temperature distribution inside the specimens when they are heated onone side without loads, and at the same time, a RC beam strengthened by theCMMR with the U style is made to measure the temperature distribution when it isheated on three sides without loads(3) The shear behavior of the strengthened beams in both the normaltemperature and the elevated temperature is studied by experiments. The experiments studied the shear behavior of the strengthened beams effected by different factors by changing the style of the strengthening method and the thickness of the strengthening layer.(4) The shear mechanism of the strengthened beams is discussed. It is assumed that the shear mechanism of CMMR is consistent with the web, also based on the The truss-arch model, the equivalent section is introduced according to the distribution of the temperature in the section of the specimens.At last, a method is put forward to calculate the shear capacity of the RC beams strengthened by the CMMR in the elevated temperature.(5) The article expatiates on the measures to strength shear resistance of RC beams by CMMR and put forward some suggestions and experiences.